Reduction of the cement content in rendering mortars with fine glass aggregates

The viability of the reduction of the cement content of coating mortars with simultaneous incorporation of very fine glass aggregates, without jeopardizing their functional performance, is discussed here. The use of these modified mortars has both environmental and economic potential advantages. In fact less energy is needed to produce cement and the direct cost of mortar production is lower. To evaluate the eventual pozzolanic properties of glass fines an experimental programme was followed comprising a series of tests to characterize the behaviour of these mortars in terms of mechanical strength, water-related behaviour, durability and other properties. The results were extremely positive, well above initial expectations. As a matter of fact, it was clearly demonstrated that the mortar with 1:5 cement:aggregate (considering aggregate as sand + glass fines) ratio instead of 1:4 and 20% incorporation of fine glass aggregates complies with all the requirements to be used as a coating mortar. Since screening of construction and demolition waste and solid urban waste is presently established, it is possible to crush glass waste and upscale the production of pre-mixed mortars with glass incorporation. This will allow a reduction of the cement content of these modified mortars and result in environmental benefits, both in terms of energy needed to produce cement and corresponding emissions to the atmosphere, and reduction of dumped waste.